My interest in the genre came from finding out about the development of LOTRO, since I was and still am a big LOTR fan. I signed up in some fansite for fellow Spanish-speaking players and became an active part of its community even 2 years before its actual launch. Made some friends there and tried some games with them while we waited for the launch. My first taste of the genre was a free weekend in World of Warcraft (Steamwheedle Cartel server, I remember that), but the one I really played extensively for many months and actually bought was Guild Wars (not really a MMO but whatever).
After that, came LOTRO itself, my one true love. Then SWTOR during three intense years, but I ended up developing a very complicated and toxic love/hate relationship with that one and I haven't even touched it since 4.0. and that was ten years ago. Can't stand level scaling.
I bought GW2 with great expectations after the first game but it just never clicked with me. It's just too different.
Ever since the launch of WoW Classic that's basically all I play, especially after Hardcore mode became a thing. I've played classic far more than I ever played the actual game at its different expansions and iterations when they were new. I'll eventually return to LOTRO, but I always seem to be busy with other stuff when Legendary Servers start and I don't want to feel left behind.